RHINCALANUS GIGAS 343 



November 193 1 in this region; but from the middle of November (St. 1 031) to the end 

 of December (St. 1085) we find everywhere a mature stock consisting entirely of adults, 

 with a few stage v — usually less than 20 per cent. 



Some of the stations, for which the stock curves are shown in Fig. 27, were 

 taken in Weddell Sea water (Sts. 1029, 1031, 1033, 1048, 1050, 1052, 1073, 1076 and 

 1085, Fig. 2 a). The remainder, except 1021 in South Atlantic water near the 

 Falklands, were taken in the Bellingshausen Sea current (1054, 1056, 1063, 1066 and 

 1083, Fig. 2 a). Sts. 1029, 1052, 1073, 1076 and 1085 were taken in the "oldest" type of 

 Weddell Sea water (average of o-ioo m. between o and i-o° C). 



At Sts. 1029, 1052 and 1085, in the "oldest " Weddell Sea water, we find a high 

 proportion of stage v in the upper nets, and, while the lower haul at St. 1029 was not 

 analysed into stages, the lower hauls at Sts. 1052 and 1085 consisted of adults with 

 some stage v, less than 25 per cent. At St. 1052, and to a lesser extent 1076, the 

 proportion of adult males in the lower nets was high, and at these stations it is probably 

 correct to assume that the population was a mixture of the populations of the Bellings- 

 hausen Sea current and the Weddell Sea current. St. 1073 was a shallow inshore station 

 at which only a surface haul was made. It is apparent, however, that in this season, 

 as in the previous one, the stock in the "oldest" Weddell Sea water is not yet 

 mature, while it has reached maturity at stations in the Bellingshausen Sea current 

 proper. This is shown by the high proportion of stage v in the population at Sts. 1029, 

 1052 and 1085. One must again assume that something has occurred to prevent that 

 part of the stock originating in the Bellingshausen Sea current from attaining maturity, 

 and that the action of water colder than i-o° C. has possibly been to retard the develop- 

 ment of the stages. 



Sts. 103 1, 1033, 1 04 1, 1045, 1048 and 1050 were taken in Weddell Sea water of which 

 the average temperature was less than 0° C, that is water carrying unmelted or melting 

 pack-ice or water in which ice had recently melted. The population at St. 1033 is per- 

 haps again a mixture of the Bellingshausen Sea and Weddell Sea stock, and here the 

 proportion of aduh males in the lower nets is rather high (13-8 per cent). At the other 

 stations the stock is probably purely of Weddell Sea origin. At Sts. 1041 and 1045 

 the catches of Rhincalamis were too small for satisfactory analysis into stages and the 

 copepod fauna at these stations was made up of species other than R. gigas, mainly 

 Calanus acuitis and C. propmqmis. Sts. 103 1, 1048 and 1050, however, show a mature 

 population which consisted of adults and a few stage v, as was found in this type of 

 water in the previous season (January 1932). This, if our conclusions drawn from the 

 stock curves of the previous season are correct, is a population which has failed to spawn 

 and which originated outside the Weddell Sea, possibly from the previous winter's 

 spawning. It was carried into the Weddell Sea in the warm deep water of the East Wind 

 Drift current, and has risen from the deep water into the surface water during its passage 

 through the Weddell Sea in the north-easterly current. 



With regard to the appearance of males during this season, we have already seen that 

 the proportion of adult males was high at Sts. 1052 and 1076 in the "oldest" type 



